BEC Posted December 2, 2006 Share Posted December 2, 2006 Since I recently acquired some K-77Fs and have some K-77Ms around, thought I would see how they compare. I plotted a FR curve for both. Both were driven by an HP sweep generator at 3500 to 20 Khz. No cap or amp was used, the sweep generator directly drove both of them at 1 volt. The dip at 13 Khz on the K-77F seems to really be there at least in the one I tested. I thought at first it was probably a reflection, but since the K-77M was in exactly the same place during its test and tested exactly the same way and does not have the dip, I think the dip is really there (at least on this particular K-77F). Quote Link to comment Share on other sites More sharing options...
Duke Spinner Posted December 2, 2006 Share Posted December 2, 2006 geez ... those curves... make the Altec 802/806/902 drivers look pretty amazing ...... [:|] Quote Link to comment Share on other sites More sharing options...
consistent Posted December 2, 2006 Share Posted December 2, 2006 What a drop! Bob, how do your tweets compare with these plots? Cheers Quote Link to comment Share on other sites More sharing options...
BEC Posted December 2, 2006 Author Share Posted December 2, 2006 Mine go right up to 20 khz. Bob Quote Link to comment Share on other sites More sharing options...
garyrc Posted December 3, 2006 Share Posted December 3, 2006 BEC, Thanks for all of your informative posts. Did your measuring equipment cost you an arm and a leg? I'm searching for a good way to make both nearfield speaker measurements, and farfield room measurements. The Radio Shack meter has got to go! I back ordered a Beherenger measurement mic, and will try some online analyzers, but may need something better. What do you have? Do you like it? Quote Link to comment Share on other sites More sharing options...
BEC Posted December 3, 2006 Author Share Posted December 3, 2006 It would seem to me that it would be rather easy to build a spectrum analyzer unit that would work good with a computer to do good measurements. I in fact bought one that should do the job quite well, but is really disapointing compared to real dedicated test equipment. Anyway, I have a Wavtek Model 5820B Spectrum Analyzer and an HP 3325A Frequency Generator. Both were pretty much top of the line in their day and very expensive. Probably $30,000 or more when new for the pair. I gave about $1,000 for the both of them. I use the Behringer Mic and UB802 mixer to feed the spectrum analyzer. I drive an old HP pen plotter with the output of the Wavtek. So not too badly expensive as long as you can manage to find good used ones. The tough thing about the used spectrum analyzers is that most of the ones on the market are for higher than audio frequencies. You really have to find one that can resolve the audio spectrum about full screen. Bob Quote Link to comment Share on other sites More sharing options...
John Warren Posted December 4, 2006 Share Posted December 4, 2006 After seeing the response I was curious to see how the Klipsch AA, AK, AK-2 and AK-3 tweeter filters affect the voltage to the tweeter. The result is below. Top graph is the model of the total impedance for a T35 calibrated against measurement. This became the load for the filters (bottom graph). Klipsch choses a tweeter crossover point (about 6kHz) that is about an octave above Fs (~3kHz). Quote Link to comment Share on other sites More sharing options...
garyrc Posted December 7, 2006 Share Posted December 7, 2006 Bob, About when do you think the K-77- F you tested was made? I heard that there were some problems with the earlier ones, and that the manufacturer in the Philippines later "got it right." My earliest one (a replacement for a blown M) wasn't as good as my newer ones, by ear -- the older F was less clean and less "airy." As you know, my measurement stuff sucks at the moment, but reads consistently (though wrong?) so my measurements may mean nothing except in the relative levels when changing speakers, but with the test bands from the Stereophile Critics' Choice disk, test section, nearfield (2' on axis), my old F (c 2002 ?) droops comparatively (~~ 2 dB, center of fairly symmetrical needle swing), at the band centered at 12.5 K Hz, and continues to droop just a little more up to 16 K, which is down about 3.5 dB. My more recent configuration F is about flat at 10K, then has just a 1 dB droop at 12.5 KHz, then goes back up to flat at the band centered at 16K. At 20K, both vintages of F and my one remaining M are all down about 8 dB, or more, in the case of the early F. Quote Link to comment Share on other sites More sharing options...
BEC Posted December 7, 2006 Author Share Posted December 7, 2006 I think the one I tested was from 2004. I don't think there is a way to make that design go higher than the K-77M really. And Klipsch only claims the new Khorn's frequency response up to 17 khz. The K-77F is simply a clone of the K-77M and there would be no reason to expect it to be better than the K-77M. The different K-77Ms I have tested vary quite a bit in frequency response and sensitivity. I think that would be true also of the K-77F. I think from the ones I have seen the inside of, the K-77F might be improved a bit by installing a new EV diaprhagm. The EV diaphragm looks to be a lot better constructed than the clone of the EV diaphragm that the K-77F uses. I do have a bunch of brand new in the box T-35As (K-77M) made toward the end of EV manufacture of those. I probably should test one of those to see how a brand new never used fresh from the factory one tests. Bob Crites Quote Link to comment Share on other sites More sharing options...
consistent Posted December 7, 2006 Share Posted December 7, 2006 When you do the test throw in your tweeter Bob, I'd like to compare scans to what I hear. Cheers Quote Link to comment Share on other sites More sharing options...
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